Technology

“Red Tide” algae treating sewage in Hong Kong

A laboratory scientist at Hong Kong’s Open University monitors algae activity under a microscope.

heung Chi-fai writes in the South China Morning Post that a top research team from the Open University in Hong Kong has been encouraged by the government to test an emerging technology that uses algae to treat sewage and produce fuel.

Led by Professor Ho Kin-chung, dean of the university’s school of science and technology, the team plans to use local species of algae to test a treatment method that could one day be used to produce energy, purify water and reduce waste.

Ho, an expert in the rapid growth of certain algae that cause red tides, hopes to secure HK$10 million ($1.29 million USD) from the government’s Innovation and Technology Fund for a pilot scheme at a treatment works in North District which he said could help Hong Kong diversify its economy.

The public in Hong Kong often associates algae blooms with the 1998 red-tide disaster that wiped out 80 per cent of fish farm stock, but Ho said many blooms were useful. Since algae feed on nutrients such as phosphorous and nitrogen, they can help remove pollutants from sewage and minimize the generation of sludge, he said.

According to the researchers, the algae they have studied could comprise up to 30 per cent oil. Ho said the exponential growth of the single-cell algae could quickly create a bloom mature enough for oil harvest.

Ho acknowledged that putting the idea into practice might be challenging both financially and logistically. “The problem is not with the theory. The real difficulty is how to industrialize it, making it cost-effective so that investors feel confident to make a bet on us.”

The team estimates that just a single ton of oil could be harvested from an average 2.5-hectare algae farm per day. So algae must be farmed in a more efficient and cheaper way, said Ho. But he said the process should deliver a variety of benefits that would make it economically viable, including sewage treatment and water purification. In addition, the algae naturally carry out photosynthesis – absorbing carbon and releasing oxygen – which would be good for the environment.

Tests are being carried out inside and outside the university’s laboratory – which houses the city’s largest bank of local algae species – to find out which are the most useful for oil extraction, how to grow the organisms in various environments and how to harvest them cost-effectively.

Ho said Hong Kong, with its subtropical climate and seaside location, was an ideal place to grow algae. The team has collaborated with a top engineer from the United States to set up an algae farm in Daya Bay. A mainland-based fish farmer had also agreed to give over large sections of his farm to carry out water-purification tests using algae, Ho said.

A spokesman for the Drainage Services Department said they had preliminarily given Ho’s team the green light to carry out the pilot scheme at the Shek Wu Hui sewage treatment plant.